Multiplexing large payloads of control information from user equipments

ABSTRACT

Disclosed is multiplexing transmissions of Uplink Control Information (UCI) signals having variable payloads from User Equipments (UEs). The UCI transmission uses a first format type if its size is less than or equal to a predetermined values and it uses a second format type if its size is greater than a predetermined value. When the first format type is used the UE multiplexing is through a first method while when the second format type is used the UE multiplexing is through a second method which is different than the first method. The structure of the second format type is the same as the structure used for the transmission of data information by UEs. The UEs can also be grouped and UCI transmission can be triggered through the reception of control signaling addressing a group of UEs and indicating UCI transmission by a sub-group of UEs in the group of UEs.

PRIORITY

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/172,432, entitled “MultiplexingTransmissions of Channel State Information”, which was filed on Apr. 24,2009, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to wireless communication systems and,more particularly, to multiplexing transmissions conveying largepayloads of control information from user equipments.

2. Description of the Related Art

A communication system consists of a DownLink (DL), supportingtransmissions of signals from a base station (Node B) to User Equipments(UEs), and of an UpLink (UL), supporting transmissions of signals fromUEs to the Node B. A UE, also commonly referred to as a terminal or amobile station, may be fixed or mobile and may be a wireless device, acellular phone, a personal computer device, etc. A Node B is generally afixed station and may also be referred to as a Base Transceiver System(BTS), an access point, or some other terminology.

The DL signals consist of data signals, carrying the informationcontent, control signals providing Downlink Control Information (DCI),and Reference Signals (RS) which are also known as pilots. The Node Btransmits DCI through a Physical Downlink Control CHannel (PDCCH) anddata information through a Physical Downlink Shared CHannel (PDSCH).

The UL signals consist of data signals, carrying the informationcontent, control signals providing Uplink Control Information (UCI), andReference Signals (RS). The UEs convey UL data signals through aPhysical Uplink Shared CHannel (PUSCH). UCI signals includeacknowledgement signals associated with the application of a HybridAutomatic Repeat reQuest (HARQ) process, Service Request (SR) signals,Channel Quality Indicator (CQI) signals, Precoding Matrix Indicator(PMI) signals, and Rank Indicator (RI) signals. The combination of CQI,PMI, and RI will be referred to as Channel State Information (CSI). UCIcan be transmitted in a Physical Uplink Control CHannel (PUCCH) or,together with data, in the PUSCH.

The CSI is used to inform the Node B of the channel conditions the UEexperiences in the DL in order for the Node B to select the appropriateparameters, such as the Modulation and Coding Scheme (MCS), for thePDCCH or PDSCH transmission to the UE and ensure a desired BLock ErrorRate (BLER) for the respective information. The CQI provides a measureof the Signal to Interference and Noise Ratio (SINR) over sub-bands orover the whole operating DL BandWidth (BW), typically in the form of thehighest MCS for which a predetermined BLER target can be achieved for asignal transmission by the Node B in the respective BW. The PMI and RIare used to inform the Node B how to combine a signal transmission tothe UE from multiple Node B antennas in accordance with theMultiple-Input Multiple-Output (MIMO) principle. Full channel stateinformation in the form of channel coefficients allows the selection ofthe precoding weights with MIMO to closely match the channel experiencedby the UE and offer improved DL performance at the expense of increasedUL overhead required to feedback the channel coefficients relative toother CSI signal types.

An exemplary structure for the PUSCH transmission in the UL TransmissionTime Interval (TTI), which for simplicity is assumed to consist of onesub-frame, is shown in FIG. 1. The sub-frame 110 includes two slots.Each slot 120 includes N_(symb) ^(UL) symbols used for the transmissionof data signals, control signals, or RS. Each symbol 130 furtherincludes a Cyclic Prefix (CP) to mitigate interference due to channelpropagation effects. The PUSCH transmission in one slot may be locatedat the same or at a different part of the operating BW than the PUSCHtransmission in the other slot. Some symbols in each slot can be usedfor RS transmission 140 to provide channel estimation and enablecoherent demodulation of the received signal. The transmission BW isassumed to consist of frequency resource units which will be referred toas Physical Resource Blocks (PRBs). Each PRB is further assumed toconsist of N_(sc) ^(RB) sub-carriers, or Resource Elements (REs), and aUE is allocated M_(PUSCH) PRBs 150 for PUSCH transmission for a total ofM_(sc) ^(PUSCH)=M_(PUSCH)·N_(sc) ^(RB) REs for the PUSCH transmissionBW.

An exemplary UE transmitter block diagram for UCI and data transmissionin the same PUSCH sub-frame is illustrated in FIG. 2. Coded CQI bits 205and coded data bits 210 are multiplexed 220. If HARQ-ACK bits also needto be multiplexed, data bits are punctured to accommodate HARQ-ACK bits.Discrete Fourier Transform (DFT) of the combined data bits is performedin DFT unit 230. UCI bits are then obtained by performing sub-carriermapping in sub-carrier mapping unit 240, wherein the REs correspondingto the assigned transmission BW are selected in control unit 250.Inverse Fast Fourier Transform (IFFT) is performed in the IFFT unit 260.Finally the CP is inserted in CP Insertion unit 270 and filtering isperformed in Time Windowing unit 280, which outputs the transmittedsignal 290. For brevity, additional transmitter circuitry such asdigital-to-analog converter, analog filters, amplifiers, and transmitterantennas are not illustrated. Also, the encoding process for the databits and the CSI bits, as well as the modulation process for alltransmitted bits, are omitted for brevity. The PUSCH signal transmissionis assumed to be over clusters of contiguous REs in accordance to theDFT Spread Orthogonal Frequency Multiple Access (DFT-S-OFDM) methodallowing signal transmission over one cluster 295A (also known asSingle-Carrier Frequency Division Multiple Access (SC-FDMA)), or overmultiple non-contiguous clusters of contiguous BW 295B.

The Node B receiver performs the reverse (complementary) operations ofthe UE transmitter. This is conceptually illustrated in FIG. 3 where thereverse operations of those illustrated in FIG. 2 are performed. Afteran antenna receives the Radio-Frequency (RF) analog signal and afterfurther processing units (such as filters, amplifiers, frequencydown-converters, and analog-to-digital converters) which are not shownfor brevity, the received signal 310 is filtered in Time Windowing unit320 and the CP is removed in CP Removal unit 330. Subsequently, the NodeB receiver applies a Fast Fourier Transform (FFT) in FFT unit 340,selects the REs used by the UE transmitter in Sub-Carrier Demapping unit350, applies an Inverse DFT (IDFT) in IDFT unit 360, extracts theHARQ-ACK bits and places respective erasures for the data bits inExtraction unit 370, and de-multiplexes in Demultiplexer unit 380 thedata bits 390 and CSI bits 395. As for the UE transmitter, well knownNode B receiver functionalities such as channel estimation,demodulation, and decoding are not shown for brevity.

An exemplary structure for the CSI transmission in one slot of the PUCCHis illustrated in FIG. 4. A similar structure may also be used for theHARQ-ACK transmission in the PUCCH. The transmission in the other slot,which may be at a different part of the operating BW for frequencydiversity, is assumed to effectively have the same structure. The CSIsignal transmission in the PUCCH is assumed to be in one PRB. The CSItransmission structure 410 comprises the transmission of CSI signals andRS for enabling coherent demodulation of the CSI signals. The CQI bits420 are modulated in modulators 430 with a “Constant Amplitude ZeroAuto-Correlation (CAZAC)” sequence 440, for example with QPSKmodulation, which is then transmitted after performing the IFFToperation as it is subsequently described. Each RS 450 is transmittedthrough the unmodulated CAZAC sequence.

An example of CAZAC sequences is given by Equation (1)

$\begin{matrix}{{c_{k}(n)} = {\exp\left\lbrack {\frac{{j2\pi}\; k}{L}\left( {n + {n\frac{n + 1}{2}}} \right)} \right\rbrack}} & (1)\end{matrix}$where L is the length of the CAZAC sequence, n is the index of anelement of the sequence n={0, 1, . . . , L−1}, and k is the index of thesequence. If L is a prime integer, there are L−1 distinct sequenceswhich are defined as k ranges in {0, 1, . . . , L−1}. If the PRBscomprise of an even number of REs, such as for example N_(sc) ^(RB)=12,CAZAC sequences with even length can be directly generated throughcomputer search for sequences satisfying the CAZAC properties.

FIG. 5 shows an exemplary transmitter structure for a CAZAC sequencethat can be used without modulation as RS or with modulation as CSIsignal. The frequency-domain version of a computer generated CAZACsequence, generated in CAZAC Sequence generator 510, is used. The REscorresponding to the assigned PUCCH BW are selected in Control unit 520for mapping in Sub-Carrier Mapping unit 530 the CAZAC sequence. An IFFTis performed in IFFT unit 540, and a Cyclic Shift (CS), as it issubsequently described, is applied to the output in Cyclic Shift unit550. Finally, the CP is inserted in CP Insertion unit 560 and filteringis performed in Time Windowing unit 570, which outputs transmittedsignal 580. A UE is assumed to apply zero padding in REs used for signaltransmission by other UEs and in guard REs (not shown). Moreover, forbrevity, additional transmitter circuitry such as digital-to-analogconverter, analog filters, amplifiers, and transmitter antennas as theyare known in the art, are not shown.

The reverse (complementary) transmitter functions are performed for thereception of the CAZAC sequence. This is conceptually illustrated inFIG. 6 where the reverse operations of those in FIG. 5 apply. An antennareceives RF analog signal and after further processing units (such asfilters, amplifiers, frequency down-converters, and analog-to-digitalconverters) the digital received signal 610 is filtered in TimeWindowing unit 620 and the CP is removed in CP Removal unit 630.Subsequently, the CS is restored in the CS Restore unit 640, and a FastFourier Transform (FFT) is performed in FFT unit 650. The transmittedREs are selected in Sub-Carrier Demapping unit 660 under control ofControl unit 665. FIG. 6 also shows the subsequent correlation inMultiplier 670 with the replica of the CAZAC sequence produced in CAZACBased Sequence unit 680. Finally, the output 690 is obtained which canthen be passed to a channel estimation unit, such as a time-frequencyinterpolator, in case of a RS, or can to detect the transmittedinformation, in case the CAZAC sequence is modulated by CSI informationbits.

Different CSs of the same CAZAC sequence provide orthogonal CAZACsequences. Therefore, different CSs of the same CAZAC sequence can beallocated to different UEs in the same PRB for their RS or CSItransmission and achieve orthogonal UE multiplexing. This principle isillustrated in FIG. 7. In order for the multiple CAZAC sequences 710,730, 750, 770 generated respectively from multiple CSs 720, 740, 760,780 of the same root CAZAC sequence to be orthogonal, the CS value 790should exceed the channel propagation delay spread DELTA (including atime uncertainty error and filter spillover effects). If T_(S) is theDFT-S-OFDM symbol duration, the number of such CSs is equal to themathematical floor of the ratio T_(S)/D.

For the CSI transmission structure in the PUCCH sub-frame, asillustrated in FIG. 4, for one of the two sub-frame slots, 5 symbolscarry CSI and 2 symbols carry RS. As the CSI transmission needs to berelatively reliable and cannot utilize HARQ retransmissions, it needs tobe protected through reliable channel coding. As a result, the CSIpayload supported in the PUCCH is small. For example, puncturing a (32,10) Reed-Mueller (RM) code to (20, 10), 10 CSI bits can be transmittedusing QPSK modulation and coding rate of ½ (20 coded bits).

In order to support higher data rates than possible in legacycommunication systems, aggregation of multiple Component Carriers (CCs)can be used in both the DL and the UL to provide higher operating BWs.For example, to support communication over 100 MHz, aggregation of five20 MHz CCs can be used. UEs capable of operating only over a singleDL/UL CC pair will be referred to as “Legacy-UEs (L-UEs)” while UEscapable of operating over multiple DL/UL CCs will be referred to as“Advanced-UEs (A-UEs)”. The invention assumes that if an A-UE receivesPDSCH in multiple DL CCs or transmits PUSCH in multiple UL CCs, adifferent data packet having its own HARQ process is conveyed by eachsuch PDSCH or PUSCH transmission.

FIG. 8 further illustrates the principle of CC aggregation. An operatingDL BW of 100 MHz 810 is constructed by the aggregation of 5 (contiguous,for simplicity) DL CCs, 821, 822, 823, 824, 825, each having a BW of 20MHz. Similarly, an operating UL BW of 100 MHz 820 is constructed by theaggregation of 5 UL CCs, 831, 832, 833, 834, 835, each having a BW of 20MHz. Each DL CC is assumed to be uniquely mapped to a UL CC (symmetricCC aggregation) but it is also possible for more than 1 DL CC to bemapped to a single UL CC or for more than 1 UL CC to be mapped to asingle DL CC (asymmetric CC aggregation, not shown for brevity). Thelink between DL CCs and UL CCs can be UE-specific.

To improve cell coverage and increase cell-edge data rates in the DL,Coordinated Multiple Point (CoMP) transmission/reception through JointProcessing (JP) can be used where multiple Node Bs transmit the samedata signal to a UE. The DL CoMP principle is illustrated in FIG. 9wherein two Node Bs, Node B1 910 and Node B2 920, transmit a first datasignal to UE1 930 and a second data signal to UE2 940. The Node Bs sharethe information content for a UE operating in DL CoMP mode throughbackhaul which is typically referred to as X2 interface 950. Thebackhaul, for example, may be a fiber optic link or a microwave link.

To support PDSCH reception by an A-UE over multiple DL CCs, the A-UEshould be able to transmit substantially larger CSI or HARQ-ACKinformation payloads to the Node B than an L-UE having PDSCH receptiononly in a single DL CC. While for symmetric DL/UL CC aggregations UCItransmission may fundamentally appear just as a parallelization of theone for single DL/UL CC pair to multiple DL/UL CC pairs, it is insteadpreferable for a UE to transmit all UCI in only one UL CC. This allowsaddressing all possible UE-specific symmetric or asymmetric DL/UL CCaggregations with a single design. It also avoids Transmission PowerControl (TPC) problems that may occur if the UE simultaneously transmitsUCI signals with substantially different powers in different UL CCs.Therefore, it is advantageous to consider UCI signaling structures wherethe transmission is in a single UL CC. This further necessitates thetransmission of larger UCI payloads, than legacy ones, in a singlechannel.

DL CoMP also represents a challenging scenario with respect to requiredpayloads of CSI feedback signaling. Even for the benign case of CQI-onlyfeedback, the respective payload increases proportionally with thenumber of Node Bs in the CoMP CSI reporting set. For example, for 3 NodeBs in the CoMP CSI reporting set, the total CSI payload is 30 bits andcannot be supported by the PUCCH structure in FIG. 4. Since a CoMP UE isoften likely to also experience low UL SINR, supporting higher CSIpayloads becomes even more challenging. The combination of CoMP andmultiple DL CCs further increases the required CSI payloads.

The PUSCH can support substantially larger payloads than the PUCCH andcan accommodate the increased UCI payloads. However, as the minimumPUSCH granularity is 1 PRB, the UL overhead from using conventionalPUSCH to support only UCI transmissions can become substantial even whenthis is done for a few UEs per sub-frame.

Therefore, there is a need to design PUCCH structures supporting largepayloads for UCI signaling in a communication system supporting DL CCaggregation or DL CoMP.

There is another need to minimize the UL overhead corresponding to thetransmission of large UCI payloads.

Finally, there is a need to efficiently manage the PUCCH and PUSCHresources while supporting the transmission of large UCI payloads.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been designed to solve at leastthe aforementioned limitations and problems in the prior art and thepresent invention provides methods and apparatus for using differentchannel structures for the transmission of Uplink Control Information(UCI) according to the UCI payload, for multiplexing UCI transmissionsfrom User Equipments (UEs) in the selected channel structure, and formanaging the resources associated with UCI transmissions from differentUEs.

In accordance with a first embodiment of the present invention, periodicUCI transmission in a Physical Uplink Control CHannel (PUCCH) uses afirst PUCCH format if the UCI payload is less than or equal to apredetermined value and uses a second PUCCH format if the UCI payload isgreater than the predetermined value. The second PUCCH format has thesame structure as the one used for the transmission of data informationby UEs.

In accordance with a second embodiment of the present invention, UCItransmissions from multiple UEs are multiplexed in the second PUCCHformat using either Time Division Multiplexing (TDM) or FrequencyDivision Multiplexing (FDM). The UEs also transmit Reference Signals(RS) which are multiplexed in the same time-frequency resources usingdifferent cyclic shifts of a Constant Amplitude Zero Auto-Correlation(CAZAC) sequence.

In accordance with a third embodiment of the present invention, a Node Bassigns UEs into UCI groups with each UCI group having an identity. UCItransmission by UEs in a UCI group is activated through the reception ofa Downlink Control Information (DCI) format containing the UCI groupidentity. The DCI format also contains a bit-map wherein at least onelocation in the bit-map is associated with one UE in the UCI group. Ifthe value of the bit-map in a reference location equals to one, therespective UE transmits the corresponding UCI type; otherwise notransmission occurs. The resources for the UCI transmission arepredetermined for each UE and can be linked to the location in thebit-map associated with the UE. A UE may belong to multiple UCI groups.The DCI format with the UCI group identity can be designed to have thesame size as another DCI format the UEs decode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a sub-frame structure for PUSCHtransmission;

FIG. 2 is a block diagram illustrating a transmitter structure for thetransmission of data information and control information in the PUSCH;

FIG. 3 is a block diagram illustrating a receiver structure for thereception of data information and control information in the PUSCH;

FIG. 4 is a block diagram illustrating a sub-frame structure for CQItransmission in the PUCCH;

FIG. 5 is a block diagram illustrating a transmitter structure for aCAZAC sequence;

FIG. 6 is a block diagram illustrating a receiver structure for a CAZACsequence;

FIG. 7 is a diagram illustrating multiplexing of CAZAC sequences throughthe application of different cyclic shifts;

FIG. 8 is a diagram illustrating the principle of Carrier Aggregation(CA);

FIG. 9 is a diagram illustrating the application of the Downlink CoMPprinciple;

FIG. 10 is a diagram illustrating exemplary CSI contents for 3 DownlinkComponent Carriers;

FIG. 11 is a diagram illustrating the concept of using multiple PUCCHformats to transmit UCI according to its payload;

FIG. 12 is a diagram illustrating Time Division Multiplexing (TDM) of 2UEs in a PUCCH format having the PUSCH sub-frame structure;

FIG. 13 is a diagram illustrating Time Division Multiplexing (TDM) of 3UEs in a PUCCH format having the PUSCH sub-frame structure;

FIG. 14 is a diagram illustrating Time Division Multiplexing (TDM) of 4UEs in a PUCCH format having the PUSCH sub-frame structure;

FIG. 15 is a diagram illustrating Frequency Division Multiplexing (FDM)of 2 UEs in a PUCCH format having the PUSCH sub-frame structure;

FIG. 16 is a diagram illustrating Time Division Multiplexing (TDM) andFrequency Division Multiplexing (FDM) of 4 UEs in a PUCCH format havingthe PUSCH sub-frame structure;

FIG. 17 is a block diagram illustrating a transmitter for UCItransmission using a PUCCH format having the PUSCH sub-frame structure;

FIG. 18 is a block diagram illustrating a receiver for UCI transmissionusing a PUCCH format having the PUSCH sub-frame structure;

FIG. 19 is a block diagram illustrating a transmission process for thePDCCH CSI format from the Node B;

FIG. 20 is a block diagram illustrating a reception process for thePDCCH CSI format from a UE;

FIG. 21 is a diagram illustrating the 1-to-1 mapping between the UEs ina CSI group and the bits in the PDCCH CSI format bit-map; and

FIG. 22 is a diagram illustrating the processing of the bit-mapinformation by a UE in the CSI group addressed by a respective PDCCH CSIformat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of the invention to those skilled in the art.

Additionally, although the present invention is described in relation toan Orthogonal Frequency Division Multiple Access (OFDMA) communicationsystem, it also applies to all Frequency Division Multiplexing (FDM)systems in general and to Single-Carrier Frequency Division MultipleAccess (SC-FDMA), OFDM, FDMA, Discrete Fourier Transform (DFT)-spreadOFDM, DFT-spread OFDMA, SC-OFDMA, and SC-OFDM in particular.

In order to support larger UCI payloads than in a legacy systemoperating with single DL/UL CCs and without DL CoMP, the supportable UCIpayload sizes need to be expanded. The first object of the presentinvention considers the definition of a PUCCH format using the PUSCHtransmission structure. The embodiment considers the CSI transmission.

FIG. 10 illustrates CSI content for 3 DL CCs 1010 consisting of {CQI 1,PMI 1, RI 1} 1020, {CQI 2, PMI 2, RI 2} 1030, and {CQI 3, PMI 3, RI 3}1040, and of the CSI for 2 DL CoMP cells 1060 consisting of {CQI 1, PMI1, RI 1} 1070, {CQI 2, PMI 2, RI 2} 1080. For the purposes of FIG. 10, aDL CC can be viewed as a DL CoMP cell and the reverse. Not all of the{CQI, PMI, RI} need to be included in the CSI. For example, the CSI forthe first DL CC 1020 may consist of only CQI while the CSI for thesecond DL CC 1030 may consist of only RI.

FIG. 11 illustrates the concept of using multiple PUCCH formats 1110(format 2 1110A and format 3 1110B) for CSI transmission. The structureof the PUCCH format for small CSI payloads and high UE multiplexingcapacity can be as described in FIG. 4 and will be referred to as PUCCHformat 2 1120. The structure of the PUCCH format for large CSI payloadsand lower UE multiplexing capacity can be as described in FIG. 1 for thePUSCH and will be referred to as PUCCH format 3 1130. Unlike PUCCHformat 2 for which CSI transmission is always confined to one PRB, theCSI transmission for PUCCH format 3 may be in one or more PRBs. Thetotal BW allocated in each sub-frame to the PUCCH formats for CSItransmission, in number of PRBs, can be signaled by the Node B through abroadcast channel. In the embodiment, after the BW for PUCCH formats 2and 3 is allocated, the adjacent PRBs towards the interior of theoperating BW can be used for other PUCCH transmissions 1140, such as SRor HARQ-ACK transmissions which for L-UEs are assumed to be through theuse of a PUCCH formats which will be referred to as PUCCH format 1.Subsequently, the remaining PRBs in the interior of the operating BW canbe allocated to PUSCH transmissions 1150.

Unlike PUCCH format 2 where multiple UEs, for example six UEs, can haveCSI transmission in the same PRB using different cyclic shifts of aCAZAC sequence (FIG. 4), only one UE can have CSI transmission usingPUCCH format 3 having the PUSCH sub-frame structure (FIG. 1). As aconsequence, the UL overhead resulting from the use of PUCCH format 3 issubstantially increased, for example by a factor of six.

The second object of the invention considers the multiplexing of CSItransmissions from multiple UEs in the PUCCH format 3 and establishes atrade-off between the payload size and the multiplexing capacity inorder to control the respective UL overhead. For example, a goal can beto allow flexible multiplexing of CSI transmissions from up to four UEsin PUCCH format 3 and use PUCCH format 2 for multiplexing CSItransmissions from six UEs. The supportable CSI payloads in PUCCH format3 can progressively decrease as the UE multiplexing capacity increasesand the smallest CSI payload and largest UE multiplexing capacity can beprovided by PUCCH format 2. For example, PUCCH format 3 can be used forCSI transmission of payloads above 20 bits from 1-4 UEs while PUCCHformat 2 can be used for CSI transmission of payloads of about 10 bitsfrom 6 UEs.

FIG. 12 illustrates the multiplexing of 2 UEs in PUCCH format 3 usingthe PUSCH sub-frame structure in accordance with the second object ofthe invention. The CSI feedback from 2 UEs is multiplexed in one PRB.The first UE, UE1 1210, has CSI transmission in the first part of eachslot and the second UE, UE2 1220, has CSI transmission in the secondpart of each slot. The RS from the first or the second UE 1230 istransmitted using a respective first cyclic shift or a second cyclicshift of the CAZAC sequence used in the cell. Each UE can have its ownpre-assigned MCS for the CSI feedback transmission (all transmissionparameters for CSI signaling in the PUCCH are allocated by higherlayers). Since each PRB is assumed to consist of 12 REs, each UE cantransmit 144 coded CSI bits with QPSK modulation, or 72 CSI informationbits with code rate of ½, or 64 CSI information bits and 8 CyclicRedundancy Check (CRC) bits. Such CSI payloads are substantially largerthan 10 bits CSI payload which can be supported using PUCCH format 2with code rate of ½, such as the punctured (20, 10) RM code.

In the case of UEs with moderate or high SINRs or with enhancedtransmission or reception based on respective antenna diversity, thereceived signal is reliable enough to support CSI transmission with amodulation order greater than QPSK, such as 8 PSK or QAM16, or with ahigher code rate, such as ⅔. For such UEs, CSI transmission can be inonly one slot to increase the UE multiplexing capacity in PUCCH format 3and reduce the respective UL overhead.

FIG. 13 illustrates the multiplexing of 3 UEs in PUCCH format 3 usingthe PUSCH sub-frame structure. CSI from a first UE, UE1 1310, istransmitted only in the first part of the first slot of the sub-frame,CSI from the second UE, UE2 1320, is transmitted only in the second partof the second slot of the sub-frame, while CSI from a third UE, UE31330, is transmitted in both slots of the sub-frame. The position ineach slot of the CSI transmission from each UE is exemplary. The RS 1340from UE1 and UE2 and the RS 1350 for UE2 and UE3 are multiplexed in therespective slots using different cyclic shifts of the same CAZACsequence.

Following the same principles, FIG. 14 illustrates the multiplexing of 4UEs in PUCCH format 3 using the PUSCH sub-frame structure. CSI from afirst UE, UE1 1410, is transmitted only in the first part of the firstslot of the sub-frame, CSI from the second UE, UE2 1420, is transmittedonly in the second part of the first slot of the sub-frame, CSI from athird UE, UE3 1430, is transmitted only in the first part of the secondslot of the sub-frame, and CSI from the fourth UE, UE4 1440, istransmitted only in the second part of the second slot of the sub-frame.The RS 1450 from UE1 and UE2 and the RS 1460 for UE3 and UE4 aremultiplexed in the respective slots using different cyclic shifts of thesame CAZAC sequence.

In addition to the Time Division Multiplexing (TDM) structure describedin FIG. 12 through FIG. 14, Frequency Division Multiplexing (FDM) canalso be applied as shown in FIG. 15 for the case of 2 UEs. The N_(sc)^(RB)=12 REs of one PRB 1510 are divided in a top sub-set of 6contiguous REs allocated to a first UE, UE 1 1520, and bottom sub-set of6 contiguous REs allocated to a second UE, UE 2 1530. Unlike the CSItransmission from each UE which is over half the BW of a PRB, the RStransmission 1540 from each UE occupies the entire PRB and themultiplexing is through the use of two different CSs, one CS for eachUE, of the same CAZAC sequence as it was previously described. Thereason for the RS transmission being over the entire PRB is to avoid areduction in the number of available CAZAC sequences that would resultfrom reducing their length to less than 12. Each UE transmits in boththe first slot 1550 and the second slot 1560 of the sub-frame. FDM canbe generalized to more than 2 RE clusters per PRB, the relative positionof the clusters may change on a sub-frame symbol basis or on a slotbasis (not shown for brevity). Additionally, FDM can be generalized sothat the REs allocated to each UE are not contiguous. For example, thefirst UE may be allocated REs 1, 3, 5, 7, 9, and 11 while UE2 may beallocated REs 2, 4, 6, 8, 10, and 12.

FDM can be combined with TDM as shown, for example, in FIG. 16. TheN_(sc) ^(RB)=12 REs of one PRB 1610 are again divided in a top sub-setof 6 contiguous REs allocated to a first UE, UE 1 1620, and bottomsub-set of 6 contiguous REs allocated to a second UE, UE 2 1630 in thefirst part of each slot and to a third UE, UE 3 1640, and to a fourthUE, UE 4 1650, respectively, in the second part of each slot. The RStransmission 1650 from each UE occupies the entire PRB and themultiplexing is through the use of four different CS, one CS for eachUE, of the same CAZAC sequence as it was previously described. Each UEtransmits in both the first slot 1660 and second slot 1670 of thesub-frame.

FIG. 17 illustrates a transmitter block diagram for the CSI transmissionusing the PUSCH sub-frame structure. The CSI information bits 1710 arecoded, rate matched to the allocated resources, and modulated in Coding,Rate Matching and Modulation unit 1720. A controller 1730 selects thePUSCH sub-frame symbols over which the CSI is transmitted. The DFT ofthe combined data bits, if any, and CSI bits is then obtained in DFTunit 1740, the REs are produced in Sub-Carrier Mapping unit 1750corresponding to the assigned transmission BW are selected by controlunit 175, the IFFT is performed by IFFT unit 1760 and finally the CP isinserted in CP Insertion unit 1770 and filtering is performed in TimeWindowing unit 1780, which outputs the transmitted signal 1790. Forbrevity, additional transmitter circuitry such as digital-to-analogconverter, analog filters, amplifiers, and transmitter antennas are notillustrated. The placement of the controller 1730 for the selected PUSCHsub-frame symbols with CSI transmission in the transmitter chain isexemplary and another location may instead be used (for example, thecontroller 1730 may be placed immediately after the CP insertion 1770).

FIG. 18 illustrates a receiver block diagram for the CSI transmittedusing the PUSCH sub-frame structure. The reverse (complementary)operations of FIG. 17 are performed. After an antenna receives theRadio-Frequency (RF) analog signal and after further processing units(such as filters, amplifiers, frequency down-converters, andanalog-to-digital converters) which are not shown for brevity, thedigital signal 1810 is filtered in Time Windowing Unit 1820 and the CPis removed in CP Removal unit 1830. Subsequently, the receiver unitapplies a FFT in FFT unit 1840, selects by Control unit 1850 the REsused by the transmitter in Sub-Carrier Demapping unit 1855, applies anIDFT in IDFT unit 1860, and selects the PUSCH sub-frame symbols overwhich the CSI is transmitted from a reference UE in control unit 1870.Then, after demodulation, rate matching, and decoding in De-Modulation,Rate-Matching and Decoding unit 1880, the CSI bits are obtained 1890. Asfor the transmitter, well known receiver functionalities such as channelestimation, demodulation, and decoding are not shown for brevity. Theplacement of the controller 1870 for the selected PUSCH sub-framesymbols with CSI transmission is exemplary and another location mayinstead be used (for example, the controller 1870 may be placedimmediately before the CP removal unit 1820). Note that for both the RStransmission and the RS reception, the conventional transmitter andreceiver structures for CAZAC sequences respectively apply with the onlyconsideration being that more than one UE transmit RS in the same PRBusing different cyclic shifts of the same CAZAC sequence.

Therefore, the second object of the present invention provides methodand means for multiplexing the CSI transmission from up to 4 UEs in aPUCCH format having the PUSCH sub-frame structure. The tradeoff is theincreased multiplexing capacity at the expense of reduced CSI symbolspace for each UE. The multiplexing of transmissions can be generalizedto support transmissions of both CSI and data. For example, in FIG. 12,the first UE may transmit CSI while the second UE may transmit data suchas a Voice over Internet Protocol (VoIP) packet.

Although CSI transmissions with PUCCH format 3 can be either periodic ordynamic, the objective to minimize the PDCCH overhead requires thatthese CSI transmissions are periodically configured with parametersprovided to each respective UE through higher layer signaling. However,this reduces the flexibility in managing the CSI transmissions dependingon their usefulness. The third object of the present invention providesa tradeoff between having full flexibility of a CSI transmission that isdynamically scheduled per sub-frame through a respective PDCCHtransmission to a UE and having limited flexibility of a CSItransmission that is semi-statically scheduled to occur periodically inpredetermined sub-frames. A trade-off between these two extreme setupscan be achieved by grouping multiple UEs in a “CSI group”, such as forexample a group of DL CoMP UEs, and dynamically scheduling the CSItransmission of selected UEs in a CSI group, using preconfiguredtransmission parameters, through the transmission of a PDCCH formatwhich will be referred to as PDCCH CSI format.

FIG. 19 describes the PDCCH CSI format transmission from the Node B. Agroup of UEs is assigned a CSI group IDentity (ID) in 1910. The PDCCHCSI format uses the CSI group ID for identification. For example, theCRC computed in 1920 from the bit-map information from 1930 conveyed bythe PDCCH CSI format is masked by the CSI group ID though an exclusiveOR (XOR) operation in 1940. The masked CRC is then appended to thebit-map information in 1950, channel coding is applied in 1960, ratematching to the allocated transmission resources is performed in 1970,and finally the PDCCH CSI format is transmitted in 1980.

At the UE receiver the reverse operations are performed as described inFIG. 20. A received candidate PDCCH CSI format 2010 is rate de-matchedin 2020, decoded in 2030, and the masked CRC 2040 and the bit-mapinformation are extracted in 2045. The masked CRC is then unmasked byperforming the exclusive OR (XOR) operation in 2050 with the CSI groupID 2060. Then, the CRC checking is performed in 2070 and it isdetermined in 2080 whether the CRC passes 2082 or not 2084. If the CRCpasses, the candidate PDCCH CSI format is considered valid and thebit-map information is further processed by the UE in 2090. If the CRCdoes not pass, the candidate PDCCH CSI format is considered invalid andits contents are discarded from further processing in 2095.

A CSI group c consists of N_(CSI) UEs and all CSI groups are assumed tohave the same size. A UE may belong to multiple CSI groups where each ofthose CSI groups corresponds to the transmission of different CSIpayloads. A total of M_(c) resources are allocated to the CSItransmission from UEs in CSI group c. This information is known to allUEs and can be communicated by the Node B to each UE either throughbroadcast signaling or through dedicated higher layer signaling. Thebit-map information consists of at least N_(CSI) bits and its size canbe selected to be equal to the size of another PDCCH format the UEalways attempts to decode, such as for example the PDCCH formatscheduling data transmissions from the UE in the PUSCH, so that thereare no additional blind decoding operations (only an additional CRCunmasking and checking). Otherwise, the CSI PDCCH format can be paddedso that it achieves a size equal to the size of another PDCCH format theUEs always decode. The CSI PDCCH format may also contain TransmissionPower Control (TPC) commands with each TPC command associated with a UCItransmission by the respective UE. Alternatively, a separate PDCCHformat may be used to provide these TPC commands and, for the simplicityof the description, this will be assumed in the following.

Each UE is also informed through higher layer signaling of its positionin the CSI group relative to other UEs in the group and there is a1-to-1 mapping between a bit in the bit-map and a UE in the CSI group.FIG. 21 illustrates the 1-to-1 mapping between the UEs in the CSI group2110 and the bits in the PDCCH CSI format bit-map 2120. Each UE may alsobe informed of the MCS it should use for the CSI transmission for arespective CSI payload; otherwise, the MCS is assumed to bepredetermined either for each CSI group (common to all UEs in the sameCSI group) or for all CSI groups (common to all UEs in all CSI groups).The resources used for the CSI transmission are assumed to be the samefor all UEs in the same CSI group, such as for example multiplexing 1 UEin 1 PRB over 1 sub-frame for UEs in a first CSI group or multiplexing 2UEs in 1 PRB over 1 sub-frame for UEs in a second CSI group. The firstPRB used by the first CSI group, if more than 1 CSI groups exist in agiven sub-frame, may either be predetermined to be the first PRB in theoperating BW or it may be communicated to the UEs through broadcastsignaling by the Node B, or it may be informed by some predeterminedbits in the PDCCH CSI format. As previously mentioned, the size of thePDCCH CSI format 2130, which consists of N_(CSI) bit-map bits 2132 andN_(CRC) _(—) _(CSI) CRC bits masked with the CSI group ID 2134, may bethe same as the size of a PDCCH format 2140 conveying a UL SchedulingAssignment (SA) to a UE for PUSCH transmission with data and consists ofN_(UL) _(—) _(SA) bits 2142 providing the scheduling information andN_(CRC) _(—) _(UE) CRC bits masked with the reference UE ID 2144. Thatis, N_(CSI)+N_(CRC) _(—) _(CSI)=N_(UL) _(—) _(SA)+N_(CRC) _(—) _(UE).The length of the CRC for the PDCCH CSI format may be less than thelength of the UL SA PDCCH format since a smaller number of UEs willtypically attempt to decode the PDCCH CSI format.

The UE processing of the bit-map information in FIG. 19 is described inFIG. 22. It is assumed that a bit value of 0 in the bit-map indicatesthat the corresponding UE in the CSI group should not transmit CSI whilea bit value of 1 indicates CSI transmission. After successfully decodingthe candidate PDCCH CSI format and obtaining the bit-map information2210, the n^(th) UE in the CSI group determines in 2220 whether thevalue of the n^(th) bit is equal to 1. If it is not equal to 1 (i.e.2230), the UE does not transmit CSI in 2240. If it is equal to 1 (i.e.2250), the UE determines the sum m of the previous n−1 bits, if any, in2260 and transmits CSI using resource m+1 in 2270. The processing stepsneed not necessarily be in the previously described order (for example,the UE may first obtain the sum of the first n−1 bits or it may simplycompute the number of bits, in the first n−1 bits, having value 1).Nevertheless, the functionalities for determining the resource for CSItransmission at the referenced n^(th) UE are fully described by FIG. 22.

The PDCCH CSI format can be generalized to request transmission ofdifferent CSI types. For example, a first CSI type can be CQI and asecond CSI type can be the coefficients of the channel medium. For thisgeneralized PDCCH CSI format, the same principles apply as previouslydescribed, with the only exception that the bit-map now includes morethan 1 bit for each UE such as, for example, 2 bits. A UE determines theresources for the assigned type of CSI transmission, if any, byconsidering the UEs with CSI transmission of the same type having anearlier bit-map location as it was previously described for the case of1 bit per UE in the bitmap.

While the present invention has been shown and described with referenceto certain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. A method for transmitting Uplink ControlInformation (UCI) from a User Equipment (UE) to a Node B over a PhysicalUplink Control CHannel (PUCCH), in a communication system, the methodcomprising the steps of: transmitting the UCI using a first PUCCH formatif a number of UCI bits is less than or equal to a predetermined value;and transmitting the UCI using a second PUCCH format if the number ofUCI bits is greater than the predetermined value, wherein the secondPUCCH format has a same structure as a format used for transmitting datainformation.
 2. The method of claim 1, wherein the UCI is channel stateinformation or acknowledgment information associated with an applicationof a Hybrid Automatic Repeat reQuest (HARQ) process.
 3. The method ofclaim 1, wherein a transmission unit is a Physical Resource Block (PRB)and a UCI transmission with the first PUCCH format is contained in onePRB and a UCI transmission with the second format is contained in one ormore PRBs.
 4. A transmitter for transmitting Uplink Control Information(UCI) from a User Equipment (UE) to a Node B over a Physical UplinkControl CHannel (PUCCH), wherein the transmitter transmits the UCI usinga first PUCCH format if a number of UCI bits is less than or equal to apredetermined value, and transmits the UCI using a second PUCCH formatif the number of UCI bits is greater than the predetermined value,wherein the second PUCCH format has a same structure as a format usedfor transmitting data information.
 5. The transmitter of claim 4,wherein the UCI is channel state information or acknowledgmentinformation associated with an application of a Hybrid Automatic RepeatreQuest (HARQ) process.
 6. The transmitter of claim 4, wherein atransmission unit is a Physical Resource Block (PRB) and a UCItransmission with the first PUCCH format is contained in one PRB and aUCI transmission with the second format is contained one or more PRBs.